How to Control Garden Growth

About Pruning

Wait to prune oak trees, like this white oak, until late winter.

Pruning is an aspect of gardening that many people find confusing. When to prune? What to prune? How to do it? When to call in the experts?

When to prune depends on the type of plant and the reason for pruning. As a general rule, you should prune in late winter or early spring to stimulate growth and in early summer to slow growth. However, there are exceptions. Trees, shrubs, and vines that bloom in spring are blooming on branches whose flower buds have formed the previous year. They are usually pruned immediately after they finish blooming, to prevent losing this year's flowers and to stimulate fresh new growth that will produce more flowers the next year. Those that bloom in summer are usually blooming on new wood. Prune them during the following spring.

Most hedges can be pruned in any season, as needed. It is best not to prune at the very end of summer because this can promote soft, new growth that is susceptible to winter damage. You can always eliminate dead wood or a badly straggling branch. Informal blooming hedges such as forsythia and rose-of-Sharon may be pruned after blooming.

There are two types of coniferous plants that require different types of pruning. The first are those that put out their entire year's new growth all at once, in late spring. This group includes pines, spruces, and firs. They can be pruned by removing up to two-thirds of the new growth while it is still fresh and pale green. With pines, this process is called candling. Do not prune the shoots all the way back to old wood because they will not produce new shoots from those sections. Evergreens that grow throughout the summer, such as yews, arborvitae, and junipers, are pruned once in early summer and again, if necessary, later in the season. They can also be pruned more heavily, down to old wood if necessary.

What to prune depends a great deal on the effect you want to create. There are major differences between the way to prune shrubs and the way to prune trees. Except under rare circumstances, ornamental trees should be left to take their natural shape and appearance, resulting in little need for pruning. They are usually pruned only to remove damaged or diseased branches or ones that cross, rub together, or form an overly acute angle with the trunk.

Suckers (also called water sprouts) should also be removed. Suckers are upright, unbranched sprouts that often appear at the base of the tree or on the lower trunk. Sometimes the upper limbs of overly dense shade trees can be thinned to open them up, allowing more light to reach the garden below. In most cases, major pruning on a large tree should be left to a professional arborist, especially if there are electrical wires nearby. Large branches require a pruning saw and should be removed back to the trunk or a main branch. Do not leave a stub, or the healing process will take too long.

Prune low-hanging branches on a sunny day so you can see how the light changes. This way you can watch the shade lighten. You also can keep an eye on the shadows, which will dance from one side of the tree to the other, changing with the time of day and position of the sun. Their silhouettes can be a beautiful part of the garden, especially in winter when the dark shadows stand out on the white snow.

Do not prune oaks in summer. Even though this may be when you are anxious to lighten shade the most, it will make your trees susceptible to oak wilt disease. Instead, prune in late winter.

Keep reading to learn about pruning shrubs and vines.

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